Recently, with development of the information age, research has been actively conducted into a display device and, in particular, a light emitting diode (LED) display or an organic light emitting diode (OLED) has drawn attention.
Such an OLED uses an organic material that autonomously emits light and has distinctly different characteristics from a conventional liquid crystal display (LCD), a plasma display panel (PDP), or the like. In particular, a display device using an OLED is a next-generation display device and is known as a so-called bendable display and, recently, has also been widely used as a display of various portable devices such as a cellular phone, a smartphone, and a tablet personal computer (PC).
An OLED is a device that generates an electron-hole pair from an electron and a hole in a semiconductor and emits light through a recombination procedure of the electron-hole pair. Such an OLED is capable of expressing all the three primary colors of light at a relatively low driving voltage and is excellent to acquire high resolution and natural color. It may be possible to produce a large-sized display device with low expense and such a display device advantageously has bendable characteristics and high response speed
However, the above-mentioned OLED has a structure including an organic thin film and an electrode and, thus, has a problem in that the OLED is rapidly degraded when external moisture, oxygen, or the like penetrates thereinto. To overcome the problem, the OLED essentially needs a protection film that blocks moisture and oxygen.
Recently, a method of forming a protection film formed of an organic material and an inorganic material as a multiple layer by atomic layer deposition (ALD) or plasma enhanced chemical vapor deposition (PECVD) has been developed.
The ALD advantageously has a low water vapor transmission rate (WVTR) but has a problem in that it is difficult to apply it to a large-sized substrate and, in particular, throughput is extremely low when multi-layered protection film is formed. In addition, a protection film formed by the PECVD has a problem in terms of flexible characteristics due to a very thick thickness.
In addition, since multiple layer structures formed of organic and inorganic materials are formed using different deposition methods for respective layers, a deposition chamber needs to be separately installed and, thus, installation costs and installation areas are highly consumed and, in particular, throughput is highly low.